Escapement mechanism



Nov. 4, 1952 c. F. CLIFFORD ESCAPEMENT MECHANISM 2 SHEETS-SHEET 1 FiledMarch 26, 1947 1952 c. F. CLIFFORD ESCAPEMENT MECHANISM 2 SHEETS-SHEET 2Filed March 26, 1947 Patented Nov. 4, 1952 UNITED STATES PATENT OFFICEESCAPEMENT MECHANISM Application March 26, 1947, Serial No. 737,279 InGreat Britain April 18, 1939 Section 1, Public Law 690, August 8, 1946Patent expires April 18, 1959 18 Claims.

This invention relates to magnetic escapement mechanism suitable forexample for a time piece, and has for its object a simplified andimproved construction of mechanism.

According to the invention the improved magnetic escapement mechanismconsists of complementary relatively oscillating and rotating members onone of which there is at least one polar formation and on the other ofwhich there is provided a wavy magnetic path which in shape issubstantially the locus of the geometric projection of the said polarformation of the other member upon it during relative oscillation androtation and in which either or both of the two members is or arepermanently magnetised whereby torque applied to the rotary memberimpulses the relative oscillatory movement and produces escapement bycausing the polar formation to follow the said wavy path whilemagnetically locked thereto.

According to one embodiment of the invention, the improved escapementmechanism comprises two relatively movable parts, one part embodying awavy path having inclined portions between its apices and made ofmagnetically conductive material, and the other part embodying at leastone magnetised element having at least one pole adapted to follow saidwavy path, means for mounting at least one of the parts so as to providerelative rotary and oscillatory movement so that the said pole of themagnetised element may travel along the said wavy path, means for givingthe oscillatory part a natural frequency of oscillation and means forapplying a rotary torque to the rotatable part, whereby the speed ofrelative rotation is controlled by the said natural frequency ofoscillation and the applied torque impulses the oscillatory part tomaintain oscillation.

In a preferred construction, one member oscillates and the other memberrotates and carries the continuous wavy element.

For example, the escapement mechanism could comprise a magnetic elementor complementary magnetic elements, one at least of which is a pendulummovable relatively, in a predetermined path, and providing a magneticflux path in air moving along such predetermined path and a magneticconductor of wave form constituting the face of a rotatable member suchas a disc or cylinder and arranged to rotate in the path of movement ofthe said magnetic fiux, so that the axis of the wave crosses the saidpath and the parts lock magnetically therewith so that oscillation ofthe one permits rotation of the other.

In the accompanying drawings:

Fig. 1 is a perspective view of one example of an escapement mechanismmade in accordance with the invention;

Fig. 1A shows a modification of the mechanism shown in Fig. 1;

Fig. 2 is a perspective illustration of a second form of escapementmechanism made in accordance with the invention;

Figs. 3 and 4 are front and side diagrammatic views of a third form ofthe invention;

Fig. 5 shows a modification of the form shown in Figs. 3 and 4;

Fig. 6 is a perspective view showing a fourth form of the invention;

Fig. 7 is a perspective view showing a fifth form of the invention;

Fig. 8 is a perspective view showing a modification of the mechanism ofFig. 6;

Fig. 9 is a perspective view showing a sixth modification of theinvention;

9A is a theoretical diagram associated with Figs. 10 and 10A arediagrammatic plan and section showing a further modification;

Fig. 11 is a fragmentary view of an alternative conisltruction for apermanently magnetised wavy pa In one example of the invention shown inFig. l, the escapement mechanism comprises a pen.- dulum a suspended ona knife-edge fulcrum b and incorporating a block 0 of non-magneticmaterial in which is embedded a magnetic conductor d of continuouswave-like form, which at its inner periphery is substantially a sinecurve of eight complete cycles inscribed on an imaginary cylinder. Suchconductor 11 is made from an annular or washer-like disc of mild steelpressed into a wave form. A star-shaped magnet e is rotatably mountedwithin the said imaginary cylinder so that its axis is coaxial therewithwhen the pendulum is at its central position and has eight poles'e', eof alternating N and S polarity so that in any working position of thependulum such poles coincide simultaneously with corresponding points oneach cycle of the wavy path of the conductor d. This star-shaped magnete is arranged to be driven by spring or weight or other suitable meansso as to rotate inside the said imaginary cylinder and is prevented fromturning until the pendulum oscillates by reason of the magnetic lockeifect between the poles and the Wavy path of the conductor. In view ofthe angularity of the pendulum in its movement the shape of the wavyinner edge of the conductor is made such that the amplitude of theundulations is smaller near the fulcrum and increases proportionallywith the distance from the fulcrum. This variation is a refinement whichis not essential in all cases owing to the elasticity of the magneticcoupling.

In operation, rotation of the star magnet will be controlled by theperiodicity of the pendulum, the spokes of the former tracing out thesine waves on the oscillating imaginary cylinder and thus escaping i. e.rotating slowly under the control of the pendulum. If the wave form ofthe conductor is a true sine wave and if the amplitude of oscillation ofthe pendulum is precisely the same as the amplitude of such wave, thenthe rotation of the star wheel e'will be substantially of uniformvelocity. If the amplitude of oscillation of the pendulum is slightlygreater as it may be, there will be a decrease in velocity of rotationat each reversal of movement of the pendulum. The escapement action ismechanically frictionless, free from wear and silent, and the smallpower applied to the magnetic conductor d by the star Wheel willsmoothly stimulate the oscillation of the pendulum, by impulsing thesame in each direction of movement whilst the inclined portion of thewavy magnetic conductor is being traversed whilst any tendency toover-stimulating such oscillation is counteracted by increase ofmagnetic losses proportional with over-amplitude of oscillation, whichlosses would operate to reduce the amplitude of oscillation tocorrespond substantially with that of the defined wavy path.

As shown diagrammatically in section in Fig. 1A the imaginarycylindrical formation of the conductor d is given an arcuate axis d sothat the poles of the star-shaped magnet e are in all positions the samedistance from the conductor to give a substantially uniform air gap.

In another example of the invention as shown in Fig. 2, a hollowstationary cylinder ofmagnetic wire I is provided, such wire having thesame sine wave form. The wire cylinder is shown for convenience mountedin a shell f of non-magnetic material. 'Within the cylinder on a drivenspindle gis mounted a bar magnet assembly consisting of pieces h ofpermanent magnetic material attached to the ends of spring spokes h offlat section which permit oscillation in a plane in which the spindlelies as shown by the arrows 7L Obviously in principle of operation themechanism of Fig. 2 is the same as that of the mechanism firstdescribed, as the magnet assembly will oscillate substantially accordingto the natural frequency of its spring mounting and its own moment ofinertia, whilst turning slowly at the same time to follow the sine curveof the cylinder, which will preferably be of slightly barrel-like formso as to conform with the arouate path of the ends of the magnet.

As shown in Figs. 3 and 4 the pendulum 2' includes a box-like magneticstructure 2' having N and S pole pieces 2 2' and is suspended by a fiatspring 2' Associated with such pole'pieces is a rotor disc 9' carrying amagnetic conductor of wave form. Oscillation of the pendulum allows therotor to turn while thepoles i 2' follow the undulations of the magneticconductor. The principle of operation is the same as before, thependulum being impulsed by torque applied to the rotor whilst speed ofrotation of the rotor is controlled by the frequency of the pendulum.

As shown in Fig. 5, the pendulum 7c embodies a C-shaped magnet k thepoles of which are magnetically locked with a conductor m of wavy formconstructed in the form ofa cylinder rotatable about an axis m. In thisexample the wave form of the magnetic conductor embodies extensions m ofthe apices so that greater variation of amplitude of oscillation of thepen dulum is permitted.

As shown in Fig. 6 the escapement mechanism comprises a pair ofpermanent magnets n secured by opposite poles to a magneticallyconductive base and to each free pole of which is attached a reed n ofmagnetically conductive material. The two magnets collectively form asingle magnet to induce magnetic flux in the reeds. The magnetised endsof the reeds are thus magnetically locked with a wavy magnetic conductor0 mounted on a rotor by the magnetic flux which they induce therein fromthe magnets. Obviously the speed of rotation of the magnetic conductoris controlled by the natural frequency of vibration of the reeds.

As shown in Fig. 7 the mechanism comprises a rotor 10 in the form of a2-pole permanent magnet rotating within a wavy magnetic conductor qhaving three complete sine waves pivoted on a diameter in the medialplane thereof and having its frequency of oscillation'controlled by abalance hair spring q. As'in'the example of Figs. 1 and 2, the amplitudeof the undulations of the wavy conductor are proportional to thedistance from the fulcrum. The operation of the mechanism is the same"in principle, the rotor although rotating being magnetically locked tothe oscillating 'wavy conductor.

As shown in Fig. 8 the mechanism comprises a hollow rectangular springreed rto WhlCh--i$ secured a washer-like ring 1" pressed to undulatingwave form within which is mounted a star-shaped rotor s the poles ofwhich are magnetically locked to the wavy inner periphery of themagnetic conductor formed by the said ring r. In operation the verticalup and down vibration of the washer-like ring 1' allows the starshapedrotor s to escape and this latter action impulses the vibrating systemand maintains the vibration.

As shown in Fig. 9 there is provided an-escapement lever t mechanicallyconnected inthe normal way to a balance wheel u, the levercarrying awavy magnetic conductor t, the undulations of which lie on the peripheryof an-imaginary cylinder. Within the conductor t is-a star wheel 0rotatably mountedon aspindle v and urged for rotation by any suitablemeans. As shown in Fig. 9A a pole "12 of the star wheel '12 is ofsubstantial width relative to the Wavy magnetic path. The effect of suchproportions is that when the pole is located at an apex as shown dottedthere will be a magnetic lockwith a greater length of the wavy conductorthan there will be in the intermediate position, as shown in full, andconsequently there will be a reduction in the reluctance of the magneticpath between the pole and the wavy conductor and-a tendency 'to hold thelever in suchposition from which'it will initially have to be movedbythe momentum of the balance wheel on its return rotation. Theoscillating balance wheel is impulsed through the lever by the magneticlock with the poles of the star-shaped wheel'v as they follow theinclined portions of the Wavy magnetic path, as in 'all previouslydescribed examples.

As shown in Figs. and 10A adjacent, the wavy magnetic conductor w isembedded in the inner wall of a cylinder w of brass or othernon-magnetic material. On the inner surface of the said cylinder arelongitudinal ribs :1: in staggered arrangement which provide mechanicalinterference to passage of the poles except when they follow the wavypath and thus the aforesaid ribs a: mechanically obstruct rotation ofthe poles if they leave the magnetic path. Such mechanical obstructionwould not normally occur.

As shown in Fig. 11 the wavy track Y may be of channel section andpermanently magnetised so that its edges form continuous poles. Suchtrack could be used in various ways, for example in the arrangement ofFig. l, in which case the star wheel a would not be permanentlymagnetised or else would have complementary ends, such as U-shaped endswhich could be magnetised where a stronger magnetic lock is requiredwith the magnetic poles provided by the magnetised edges of the path.

It will be understood that the expression pendulum is used hereingenerically and that the term is not limited to a gravity controlledoscillating member but includes any spring balance device such asdescribed in the second example of the invention.

Other alternatives come within the scope of the invention besides thosedescribed. For example, an external magnet attached to the pendulumcould trace out a magnetic sine wave on the external surface of acylinder Which was spring driven. The magnets shown in the variousfigures, might, with advantage in some cases, be magnetised axiallyinstead of radially.

Whilst a sine curve will give a substantially smooth or continuousescapement action, the invention is not limited thereto as the wave formmay be modified if required to suit any particular conditions, withoutdeparting from the nature of the invention. The construction may also bemodified in other details without departing from the nature of theinvention.

In all cases magnetic parts which are subject to changing magneticfluxes, whether changing in density or direction, are preferably made ofa material of low hysteresis loss of which there are several materialsknown and produced for such characteristic.

What I claim is: v

1. A magnetic escapement, comprising a first member; an oscillatorymember, said members being mounted for relative rotary movement; anendless wavy magnetic band-like element on one of said members forming atrack thereon; a polar element on the other member; and means forinducing magnetic flux in said elements to couple them magnetically,said wavy element having successive apex portions disposed alternatelyon opposite sides, respectively, of a circle at substantially equaldistances therefrom, and other portions connecting successive apexportions, respectively, said other portions being onopposite sides ofsaid circle inclined to the latter and being otherwise shaped anddirected so that one element will follow the other magnetically coupledelement during substantially natural oscillation of said oscillatorymember.

2. A magnetic escapement, comprising a rotary power-driven escapemember; an oscillatory member; an endless wavy magnetic band-likeelement on one of said members forming a track thereon; and a polarelement on the other member, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said Wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of a circle at substantially equal distancestherefrom, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed to followsaid magnetically coupled polar element during substantially naturaloscillation of said oscillatory member.

3. A magnetic escapement, comprising a rotary power-driven escapemember; an oscillatory member; an endless wavy magnetic band-likeelement on one of said members forming a track thereon; and a polarelement on the other member, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of a circle at substantially equal distancestherefrom, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed to followsaid magnetically coupled polar element during substantially naturaloscillation of said oscillatory member without substantial variation inreluctance.

4. A magnetic escapement, comprising a rotary power-driven escapemember; an oscillatory member; an endless wavy magnetic band-likeelement on one of said members forming a track thereon; and a polarelement on the other member, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of a circle at substantially equal distancestherefrom, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed to followsaid polar element during substantially natural oscillation of saidoscillatory member, and said members being coordinated so as to have asubstantially uniform air gap between said elements in all workingpositions of said members.

5. A magnetic escapement, comprising a rotary power-driven escapemember; an-oscillatory member; an endless, wavy magnetic band-likeelement on one of said members forming a track thereon; and a polarelement on the other member, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of a circle at substantially equal distancestherefrom, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being curved so as to follow saidmagnetically coupled polar element during substantially naturaloscillation of said oscillatory member.

6. A magnetic escapement, comprising a rotary power-driven escapemember; a second member; a strip spring by means of which said secondmember is mounted on a support for oscillatory movement; an endless Wavymagnetic band-like element on one of said members forming a trackthereon; and a polar element on the other member, one of said elementsbeing permanently magnetised and magnetically coupled with theothereleinent; said wavy element having SUQCQSQ sive apex portionsdisposed alternately on opposite sides.,.. respectively, of a, circleatsubstantially equal distances therefrom, and otherportions connectingsuccessive apex portions, respectively, said other portions being onopposite sides of said circle inclinedto the latter and being other:

wise shapedand directed to follow said magneti Cally :coupled polarelement during substantially natural oscillation; of said secondmember.

7. A ma n t cap ents inea ro ary power-driven escape member; anoscillatory member; an endless'wavy magnetic band-like element; on oneof said members forming a track he e n a po a e men n the, he membe nd Is ne. s i nd ne gnet c flu in sa d ementstw w them-m s ally ss dr avememhar ne uq ss ve pe r iqns. sp d"v alternately on opposite sides,respectively, ofa circle at substantially equal distances therefrom,

and other portions connectingsuccessive apex:

portions, respectively, said other portions being onopposite sides ofsaid circle inclined to the latter and being otherwise, shaped anddirected to followsaid magnetically coupled polar element duringsubstantially natural oscillation of said oscillatorymember.

8. A magnetic escapement, comprising a rotary power-driven escapemember; an oscillatory member; an endless wavy magnetic band-likeelement on one of said members forming a track thereon; and a polarelement on the other member,

one of said elements being permanently magnetised and magneticallycoupled with the other element, said wavy element having successive apexportions disposed alternately on opposite sides,

respectively, of a circle at substantially equal distances therefrom,and other portions connect ing successive apex portions, respectively,said member; an endless Wavy magnetic band-like,

element on one of said members forming a track therenn; a polarelementon the other member, one of said elements being permanently magnetisedand magnetically coupled with the other element, said wavy elementhaving successive apex portions disposed alternately on opposite sides,respectively, of a circle at substantially equal distances therefrom,and other portions connecting successive apex portions, respectively,said other p ortions being on opposite. sides of said circle inclined tothe latter and being otherwise shaped and directed to follow saidmagnetically coupled polar element during substantially naturaloscillation of said'oscillatory member; and cooperating means on saidmembers, respectively, to obstruct-mechanically rotation of said rotarymember if said polar element should swerve considerably from said track.

10. A magnetic escapement, comprising a rotary power-driven escapemember; an oscillatory member, one of said members having a cylindricalsurface; anendless wavy magnetic band-like elementonthecylindricalsurface of said-one member forminga trackthereon; apolar element on-the other member, one ofsaid elements be e nen l me e ise a d, agn ically,

u l d,- tns hs-o her ele e t s id, ary re1em i havi u c s ve. e port onsd s osed. alternately on opposite sides, respectively, of a circle atsubstantially equaldistances therefrom, andother portions connectingsuccessive apex portions respectively, said other. portions beingonopposite sides of; said circle inclinegl to the, latter andbeingotherwise shaped and directed to follow said magnetically coupled polarelement duringsubstantially natural oscillation. of said oscillatorymember and staggered abutments on,

said cylindricalsurface of said one member be tween, successiveconnecting I portions, respecv lm. of saidtra k elem tqo i q me ncallyreiatire ation a d. ssi si b of the ellfictivei members it aid, oar element shou dv ervecon iderably irqm a d t a k.

1-; A ma net c ca men qin in 1 t ry ower -d iv n cape. mem er; n o s lsqry member; an endless wavy magnetic band-like elementp said rotarymember forming a track thereon; and a polar element on saidoseillatorymember, one of said elements being permanently mag-netised and vmagnetically coupled with the other velement said wavy element havingsuccessiveap x port pnsdi pose l rn t s/.1 1 11110:

site sides, respectively, of a circle at substantially equal distancestherefrom, and other portions connecti g ucc si e a ex pe ises p t v ly,s ids hsrmrt ns e n n op o i s idss sa circle inclined to thelatterandbeing otherwise shaped and directed to follow said. magnetically co pledpolareleme i dur na ls aniia v 11st: m ci ation, of, saidosci l iqr -s b-v 12. A magnetic escapement, comprising, a rotary power-drivenlescapemember; an oscillatory member; an en less a vma netie andr k lement.- nsaid osc aip y, em e o n a. track thereon; and. a po with thectherelment, said wavy elementlhav ins successive pexp rt ons dis osed aate on opposi e id slresnsctiv ly i-a ir le t qu distances therefrom,and other portions connecting successiyeapex portions, respectively,said other portions being on opposite, sides of said circleinclinedtothe latter and being otherwise s ped an directe so, tha said-r0la i menwill follow said magnetically conpled traclr ele he r ta y axis, f I saies pe member; nd an endless wavy magnetic band like element on theperiphery of said disc-like escapemernb er forming atracl z. thereon,one of said elements, be-

ing permanently magnetised and magnetically conpled with theotherelement, said wavy element having successive apex portion disposedalternately inwardly and outwardly of a concentriccircle or saidescape-member at substantially, equal distances therefrom, and" other"screens, connecting successive apex portions; respectively, said other.portionsbe ingon opposite'rjside s of said,

circle inclined to the latte coupled polar. element during,substantially natural oscillation of said oscillatory member? 1a. Amagnetieescapement,comprising a re.- tary povver edriven v clrumf-lilreescape member hay;

lar, element on said roary m m er. onel iv s d lement being er r nentlymagnetisedand magnetically coupled I r. and being otherwise shaped anddirected tofollow said magnetically {1 st reassess, siips c;1 atti ,me"her,

having a polar element and being oscillatory in a plane parallel to therotary axis of said escape member; and an endless wavy magnetic band-1ike element on the peripheral surface of said drum-like escape memberforming a track thereon, one of said elements being permanentlymagnetised and magnetically coupled with the' other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of, and being substantially equally spaced from, acircle lying in a plane at right angles to the rotary axis of saidescape member, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed to followsaid magnetically coupled polar element during substantially naturaloscillation of said oscillatory member.

15. A magnetic escapement, comprising a rotary power-driven escapemember having a polar element; another member oscillatory in a planeparallel to the rotary axis of said escap member and having a formationprovided with an interior cylindrical surface surrounding said escapemember and polar element; an endless wavy magnetic band-like element onthe interior surface of said formation forming a track thereon, one ofsaid elements being permanently magnetised and magnetically coupled withthe other element, said wavy element having successive apex portionsdisposed alternately on opposite sides, respectively, of, and beingsubstantially equally spaced from, a circle lying in a plane at rightangles to the axis of the interior cylindrical surface of saidformation, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed so thatsaid polar element will follow said magnetically coupled track elementduring substantially natural oscillation of said oscillatory member.

16. A magnetic escapement, comprising a, rotary power-driven escapemember; a polar element on said escape member, said polar element beingoscillatory in a plane parallel to the rotary axis of said escapemember; a stationary member having an interior cylindrical surfacesurrounding said escape member and polar element; an endless wavymagnetic band-like element on the interior surface of said stationarymember forming a track thereon, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of, and being substantially equally spaced from, acircle lying in a plane at right angles to the axis of the interiorcylindrical surface of said stationary member, and other portionsconnecting successive apex portions, respectively, said other portionsbeing on opposite sides of said circle inclined to the latter and beingotherwise shaped and directed so that said polar element will, duringsubstantially natural oscillation thereof, follow said magneticallycoupled track element.

17. A magnetic escapement, comprising an oscillatory member having apolar element; a r0- tary power-driven disc-like escape member; anendless Wavy magnetic band-like element on the periphery of said escapemember forming a track thereon, one of said elements being permanentlymagnetised and magnetically coupled with the other element, said wavyelement having successive apex portions disposed alternately on oppositesides, respectively, of, and being substantially equally spaced from, a,circle lying in a plane at right angles to the rotary axis of saidescape member, and other portions connecting successive apex portions,respectively, said other portions being on opposite sides of said circleinclined to the latter and being otherwise shaped and directed to followsaid magnetically coupled polar element during substantially naturaloscillation of said oscillatory member.

18. A magnetic escapement as set forth in claim 1 wherein cooperatingmeans are provided on said members respectively to obstruct mechanicalrotation of said rotary member if one of said elements should swerveconsiderably from the other magnetically coupled element.

CECIL FRANK CLIFFORD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 708,769 Inden Sept. 9, 19021,277,371 Boyle et a1 Sept. 3, 1918 1,517,008 Jones Nov. 25, 19241,788,065 ONeal Jan. 6, 1931 1,825,382 Baker Sept. 29, 1931 2,061,047Schweitzer Nov. 17, 1936 2,359,656 Lurtz Oct. 3, 1944 FOREIGN PATENTSNumber Country Date 690,365 France June 17, 1930

